Process for producing multiple recording in a single medium

ABSTRACT

THE INVENTION DESCRIBES A METHOD FOR INDIVIDUALLY RECORDING A TRANSMITTANCE IMAGE AND A REFRACTIVE INDEX IMAGE IN A SINGLE PHOTOGRAPHIC EMULSION. THE INVENTION RELATES TO A METHOD FOR RECORDING DIFFERENT IMAGES IN A SINGLE PHOTOGRAPHIC EMULSION, THE LATTER WHEN PROSSEDED IN ACCORDANCE WITH THE INVENTION PROVIDING, AMONG OTHER THINGS, A UNIQUE TYPE OF COMPLEX-VALUED SPATIAL FILTER.

April 17, 1973 FlLLMORE ET AL 3,728,118

PROCESS OF PRODUCING MULTIPLE RECORDING IN A SINGLE MEDIUM Filed Aug. 10, 1970 PREHARDEN EMULSION E WASH m H20 SENSITIZE EMULSION BY SOAKING IN DICNRONATE DRY EXPOSE T0 RECORD REFRACTIVE INDEX INAGE i WASH IN H20 BLEACHING THE EXPOSED EMULSION N 1 :WASH m H20 1 :WASH IN H20 \DRY I EXPOSE THE BLEACHED EMULSION TO RECORD THE TRANSNITTANCE INAGE DEVELOP & FIX

{WASH IN H20 w RAPID DEHYDRATION GARY L. FILLMORE RICHARD F. TYNAN 5 Y Mic- M? 4;

A GLEN T 3,728,118 PROCESS FOR PRODUCING MULTIPLE RECORD- ING IN A SINGLE MEDIUM Gary L. Fillmore, Endicott, and Richard F. Tynan, Endwell, N .Y., assignors to International Business Machines Corporation, Armonk, N.Y.

Filed Aug. 10, 1970, Ser. No. 62,473 Int. Cl. G03c 5/22, 5/26, 5/38 US. Cl. 96-48 R 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The production of complex-valued spatial filters by prior art techniques has been complex, time consuming and extremely costly. In most cases the prior art techniques require two separate emulsions, one for each image. The technique for sandwiching the separate emulsions has not been satisfactory since the methods for optically aligning the emulsions require painstaking effort and time. This problem is further aggravated by the fact that the thin emulsion surfaces are not coplanar.

Interferometric or holographic techniques have also been used to construct filters, but these require both a real object and a significant increase in the bandwidth of the filter because of the high carrier frequecies recorded.

SUMMARY OF THE INVENTION The present invention employs a novel method in which a single emulsion is exposed twice to record two different images, and by further employing conventional photographic processing techniques a complex-valued spatial filter is produced which avoids the complexities of the prior art filters. Briefly, the method of the present invention involves prehardening a photographic emulsion followed by sensitizing the photographic emulsion in a dichromate solution and thereafter exposing the emulsion to the proper illumination to record a desired refractive index image. A bleaching step follows after which the bleached emulsion is exposed to proper illumination to record the transmission image. By conventional photographic fixing techniques the transmittance image is developed, after which the emulsion is subjected to rapid dehydration to develop the refractive index image.

DESCRIPTION OF THE OBJECTS The main object is to provide a novel process for recording a plurality of different images in a single emulsion.

Another object is to provide a novel process for recording a plurality of different images in a single emulsion that, when developed, yields a complex filter that is superior in quality and less expensive than prior art filters.

A more detailed object is to provide a novel process for recording in a single photoemulsion a transmittance image and a refractive index image.

United States Patent 0 "ice A drawing in the form of a flow diagram shows the various steps of the process constituting the invention.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawing.

DESCRIPTION OF THE EMBODIMENT The novel process for recording the two different types of images will now be described with reference to the drawing. A photoemulsion, for example a Kodak 649F Spectroscopic plate, available from Eastman Kodak Company, is prehardened by soaking the emulsion plate for about ten minutes in a bath, for example Kodak SH-S, available from Eastman Kodak Company, after which the plate is removed from the bath, washed in water, and then dried. The characteristics of the Kodak 649F Spectroscopic plate are described in the publication entitled Characteristics of Kodak Plates for Scientific and Technical Applications, Kodak Pamphlet No. P-140, revised October 1968, of Eastman Kodak Company. The ingredients of the Kodak SH-S bath are described on p. 46 of the publication entitled Processing Chemicals and Formulas for Black-and-White Photography, 5th edition, 1954, first 1959 printing, of Eastman Kodak Company. More specificially, Kodak SH-S bath is an aqueous solution of the following ingredients, to wit: formaldehyde, 6-nitrobenzimidazole nitrate, sodium sulfate, and sodium carbonate. The dried emulsion plate is then sensitized by immersion, for about ten minutes, in a dichromate solution (ammonium or potassium dichromate), after which the sensitized emulsion plate is removed from the solution and dried in air.

Next, the dried sensitized emulsion is exposed to appropriate illumination to record the latent desired refractiveindex image in the sensitized gelatin portion of said emulsion and a corresponding latent silver halide density image. Following this exposure, the exposed emulsion plate is washed in running water to remove the unexposed dichromate. After which, the exposed emulsion plate is bleached by immersing the plate in Kodak E'B2 solution, available from Eastman Kodak Company, for about twelve minutes. This bleaching eliminates the latent silver image caused by the exposure, and also reduces but without destroying the sensitivity of the remaining silver halide of the emulsion to the longer wavelengths of light. If necessary, a large part of the sensitivity may be restored by soaking for a nominal period, roughly one to ten minutes, the plate in a developer solution, for example Kodak D19 developer solution, available from Eastman Kodak Company. The ingredients of the Kodak D19 developer are described on p. 38 of the aforementioned publication Processing Chemicals and Formulas for Black-and-White Photography. More specifically, Kodak D19 developer is an aqueous solution of the following ingredients, to wit: p-methylaminophenol sulfate, which is a development agent and is available from Eastman Kodak under the trade name Elon, sodium sulfite, hydroquinone, sodium carbonate, and potassium bromide. Following the bleaching operation (or after soaking in the D19 developer solution), the emulsion plate is washed in running water and thereafter dried in air. The dried emulsion plate is now exposed (for the second time) to the proper illumination distribution to record a latent desired transmittance image in the aforementioned remaining silver halide.

Typical light exposure data for the aforementioned Kodak 649F Spectroscopic emulsion, may be found, for example, in the publication entitled Data ReleaseKodak Materials for Holography, Kodak Pamphlet No. 110, February 1969, and particularly from the appropriate information at pp. 3-5 thereof. Following this exposure, the plate is subjected to normal photographic processing techniques for developing the latent density image, after which the plate is rinsed in a stop bath, and by a normal photographic fix process the transmittance image is thereby completely recorded. The aforementioned Kodak Pamphlet No. 110 describes at pp. 6 and 7 thereof typical photographic processing techniques for developing and fixing silver density images for Kodak 649F type emulsions. Following the fix step, the plate is washed in running water and then immersed in isopropyl or ethyl alcohol for a nominal period of up to two minutes to cause rapid dehydration during which the refractive image is developed, after which the plate is dried.

In the bleaching step described above, Kodak EB2 bleach has the following composition:

Mix 1 part A to 1 part B. Although this bleach provides highly satisfactory results, other bleaching solutions, commercially available, which remove the latent density image without destroying the sensitivity of the silver halide can be used.

The illumination employed in the first exposure, for the recording of the refractive index image, occupies that portion of the spectrum between ultraviolet and blue, whereas the wavelength of illumination employed in the second exposure for the recording of the transmittance image lies within the region of the original sensitvity of the emulsion. As shown from the appropriate graph on p. of the aforementioned Kodak Pamphlet No. 110, the Kodak 649F emulsion has a spectral sensitivity range between approximately .275 and .670 micron.

However, under certain conditions, the wavelength of the illumination of the aforementioned first exposure associated with recording the refractive index is between blue and ultraviolet and a longer wavelength is used for the aforementioned second exposure illumination which is associated with the recording of the transmittance den sity image. Under these conditions, the second exposure may be used to record, with reasonable success, the second image, i.e., the transmittance image, and, as such, the step of soaking the emulsion plate in the D19 solution may be dispensed with.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it Will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is: 1. A process for recording refractive index and transmittance image in a spectroscopic photographic emulsion of the type having silver halide crystals suspended in gelatin and having a predetermined spectral sensitivity range between .275 and .670 micron, said process comprising the steps of:

prehardening said emulsion by soaking said emulsion in a liquid bath containing a hardening agent;

sensitizing the prehardened emulsion by immersion of said prehardened emulsion in a solution containing a photosensitive dichromate compound;

exposing to a first illumination having a spectral content in the range between blue and ultraviolet the sensitized emulsion to record a latent refractive index image in the sensitized gelatin portion of said emulsion and a corresponding latent silver halide density image;

bleaching the exposed emulsion in a bleaching solution to remove only said silver halide density image without destroying the sensitivity of the remaining silver halide;

thereafter exposing to a second illumination having a spectral content which lies within said predetermined spectral sensitivity range the bleached emulsion to record a latent transmittance image in said remaining silver halide followed by developing and fixing, during which the transmittance image is developed; and finally rapidly dehydrating the fixed emulsion to develop the refractive index image.

2. The process as in claim 1 in which the step of prehardening the emulsion is obtained by soaking the latter for about ten minutes in said bath; and the sensitizing step is obtained by immersion for about ten minutes in said dichromate solution, said solution being of the ammonium or potassium dichromate types, and said bath being comprised of an aqueous mixture of:

formaldehyde;

6-nitrobenzimidazole nitrate;

sodium sulfate; and

sodium carbonate.

3. The process as in claim 1 in which the spectral content of said second illumination has a longer Wavelength. than that of said first illumination.

4. The process as in claim 3 further modified by the step of sensitizing the bleached exposed emulsion by soaking in a developer solution for a nominal period of time, up to twelve minutes, after which the emulsion is washed and dried prior to the recording of the transmittance image, said developer solution being comprised of an aqueous mixture of:

p-methylaminophenol sulfate;

sodium sulfite;

hydroquinone;

sodium carbonate; and

potassium bromide.

5. The process as in claim 3 in which the dehydration is carried out by immersion in alcohol, either isopropyl or ethyl, for a nominal period of about two minutes.

6. A process for recording refractive index and transmittance images in a spectroscopic photographic emulsion of the type having silver halide crystals suspended in gelatin and having a predetermined spectral sensitivity range between .275 and .670 micron, said process comprising the steps of:

prehardening said emulsion by soating the emulsion in a liquid bath containing a hardening agent, and thereafter washing in water;

sensitizing the prehardened emulsion by immersion of said prehardened emulsion in a solution containing a photosensitive dichromate compound, followed by drying;

exposing to a first illumination having a spectral content in the range between blue and ultraviolet the sensitized emulsion to record a latent refractive index image in the sensitized gelatin portion of said emulsion and a corresponding latent silver halide density image, and thereafter washing in water;

bleaching the exposed emulsion in a bleaching solution to remove only said silver halide density image with out destroying the sensitivity of the remaining silver halide, and thereafter Washing in water, followed by y thereafter exposing to a second illumination having a spectral content which lines within said predetermined spectral sensitivity range the bleached emulsion to record a latent transmittance image in said remaining silver halide followed by developing and fixing, during which the transmittance image is developed, and thereafter washing in water; and finally rapidly dehydrating the fixed emulsion to develop the refractive index image; said spectral sensivity of said second illumination being a longer wavelength than that of said first illumina- OTHER REFERENCES Lin, L. H.: Applied Optics, vol. 8, No. 5, May 1969, pp. 963-966.

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Urbach et al.: Applied Optics, vol. 8, No. 11, November 1969, pp. 2269-2281.

Mees, 1.: The Theory of the Photographic Process, 3rd ed., 1966, pp. 149, 150 and 160.

Latta, 1.: Applied Optics, vol. 7, No. 12, December 1968, pp. 2409-2416.

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CHARLES L. BOWERS, 1a., Primary Examiner US. Cl. X.R.

96--27 R, 27 H, 49, R, 50 PT, R, 6 3, 65, 68, 75, 93, 111 

